[PATCH 1/5] xfs: track deferred ops statistics

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Track some basic statistics on how hard we're pushing the defer ops.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_defer.c |   14 ++++++++++++++
 fs/xfs/xfs_trace.h        |   19 +++++++++++++++++++
 fs/xfs/xfs_trans.c        |    3 +++
 fs/xfs/xfs_trans.h        |    7 +++++++
 4 files changed, 43 insertions(+)


diff --git a/fs/xfs/libxfs/xfs_defer.c b/fs/xfs/libxfs/xfs_defer.c
index cd28b96b49ea9..bf83508edf822 100644
--- a/fs/xfs/libxfs/xfs_defer.c
+++ b/fs/xfs/libxfs/xfs_defer.c
@@ -617,6 +617,8 @@ xfs_defer_finish_one(
 	/* Done with the dfp, free it. */
 	list_del(&dfp->dfp_list);
 	kmem_cache_free(xfs_defer_pending_cache, dfp);
+	tp->t_dfops_nr--;
+	tp->t_dfops_finished++;
 out:
 	if (ops->finish_cleanup)
 		ops->finish_cleanup(tp, state, error);
@@ -679,6 +681,9 @@ xfs_defer_finish_noroll(
 
 		list_splice_init(&(*tp)->t_dfops, &dop_pending);
 
+		(*tp)->t_dfops_nr_max = max((*tp)->t_dfops_nr,
+					    (*tp)->t_dfops_nr_max);
+
 		if (has_intents < 0) {
 			error = has_intents;
 			goto out_shutdown;
@@ -720,6 +725,7 @@ xfs_defer_finish_noroll(
 	xfs_force_shutdown((*tp)->t_mountp, SHUTDOWN_CORRUPT_INCORE);
 	trace_xfs_defer_finish_error(*tp, error);
 	xfs_defer_cancel_list((*tp)->t_mountp, &dop_pending);
+	(*tp)->t_dfops_nr = 0;
 	xfs_defer_cancel(*tp);
 	return error;
 }
@@ -767,6 +773,7 @@ xfs_defer_cancel(
 	trace_xfs_defer_cancel(tp, _RET_IP_);
 	xfs_defer_trans_abort(tp, &tp->t_dfops);
 	xfs_defer_cancel_list(mp, &tp->t_dfops);
+	tp->t_dfops_nr = 0;
 }
 
 /*
@@ -830,6 +837,7 @@ xfs_defer_alloc(
 	dfp->dfp_ops = ops;
 	INIT_LIST_HEAD(&dfp->dfp_work);
 	list_add_tail(&dfp->dfp_list, &tp->t_dfops);
+	tp->t_dfops_nr++;
 
 	return dfp;
 }
@@ -942,6 +950,12 @@ xfs_defer_move(
 	struct xfs_trans	*stp)
 {
 	list_splice_init(&stp->t_dfops, &dtp->t_dfops);
+	dtp->t_dfops_nr += stp->t_dfops_nr;
+	dtp->t_dfops_nr_max = stp->t_dfops_nr_max;
+	dtp->t_dfops_finished = stp->t_dfops_finished;
+	stp->t_dfops_nr = 0;
+	stp->t_dfops_nr_max = 0;
+	stp->t_dfops_finished = 0;
 
 	/*
 	 * Low free space mode was historically controlled by a dfops field.
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 906e35eef223d..6c99bf56184b0 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -2711,6 +2711,25 @@ TRACE_EVENT(xfs_btree_free_block,
 /* deferred ops */
 struct xfs_defer_pending;
 
+TRACE_EVENT(xfs_defer_stats,
+	TP_PROTO(struct xfs_trans *tp),
+	TP_ARGS(tp),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(unsigned int, max)
+		__field(unsigned int, finished)
+	),
+	TP_fast_assign(
+		__entry->dev = tp->t_mountp->m_super->s_dev;
+		__entry->max = tp->t_dfops_nr_max;
+		__entry->finished = tp->t_dfops_finished;
+	),
+	TP_printk("dev %d:%d max %u finished %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->max,
+		  __entry->finished)
+)
+
 DECLARE_EVENT_CLASS(xfs_defer_class,
 	TP_PROTO(struct xfs_trans *tp, unsigned long caller_ip),
 	TP_ARGS(tp, caller_ip),
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 008380482777b..eb7d4272aef28 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -70,6 +70,9 @@ xfs_trans_free(
 	xfs_extent_busy_sort(&tp->t_busy);
 	xfs_extent_busy_clear(tp->t_mountp, &tp->t_busy, false);
 
+	if (tp->t_dfops_finished > 0)
+		trace_xfs_defer_stats(tp);
+
 	trace_xfs_trans_free(tp, _RET_IP_);
 	xfs_trans_clear_context(tp);
 	if (!(tp->t_flags & XFS_TRANS_NO_WRITECOUNT))
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index 2046ee06fe88f..6017efe354adc 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -151,6 +151,13 @@ typedef struct xfs_trans {
 	struct list_head	t_busy;		/* list of busy extents */
 	struct list_head	t_dfops;	/* deferred operations */
 	unsigned long		t_pflags;	/* saved process flags state */
+
+	/* Count of deferred ops attached to transaction. */
+	unsigned int		t_dfops_nr;
+	/* Maximum t_dfops_nr seen in a loop. */
+	unsigned int		t_dfops_nr_max;
+	/* Number of dfops finished. */
+	unsigned int		t_dfops_finished;
 } xfs_trans_t;
 
 /*